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Is BBT charting the key to conceiving?

"I charted religiously for 5 months, and we were doing the BD [baby dance] as soon as I saw that temp change and it just wasn't happening".  L. 

The above was a patient I saw a few years ago and I have had similar conversations with women since -  I don't believe it is uncommon to use a BBT to completely miss your fertile window!

Not sure what BBT is?  The basics:

BBT stands for Basal Body Temperature, it just means the temperature of a body at rest.

Women are cyclical creatures.  Unlike men who have a relatively stable hormone level, our hormones move through changes at different parts of our menstrual cycle, having an influence on our minds and bodies in all kinds of ways – one of which is our body temperature.  BBT charting is simply measuring your waking temp every morning, and recording it on a graph or an app.

How does a BBT chart tell me about ovulation?

Remember learning about ovulation and fertility in high school?  Probably not, because it probably wasn’t taught, but that’s an issue for another day.

Keeping it simple, estrogen is the hormone dominant in the first half of the cycle.   Estrogen can be thought of as a yin hormone and is colder.  After ovulation occurs, estrogen decreases and progesterone, a comparatively yang and warming hormone, increases.

If that makes your eyes glaze over, don’t worry.  The key takeaway here is: a rise in progesterone indicates ovulation has occurred.  A rise in progesterone is accompanied by a rise in temperature and will can be seen on a BBT chart. A chart with this temp rise is a biphasic chart, and it’s a good sign.

THE BIG QUESTION. Can you use BBT to time conception-sex?

It is vital to understand two key concepts;

  1. The rise in temperature on a BBT chart occurs AFTER ovulation.
  2. Women can conceive in the 5 days prior to ovulation and on the day of ovulation.

By the time a rise in temperature has occurred, there is little or no time for conception-sex.

Here’s where BBT charting is useful.

  1.  Nearly 15% of subfertile couples find an ovulatory dysfunction at its root [1].  It is so important to confirm that you are ovulating.
  2. Watching for patterns can help predict your window.  For example, if a temperature rises at day 15 each month, it can be assumed the fertile window opens on or near day 9.  However, this information should be used with other ovulation signs and symptoms.
  3. A TCM practitioner interprets all sorts of things in a BBT chart pertaining to hormone balance and temperature and can use this information to develop a treatment plan.  If your chart is off and not displaying a clear biphasic pattern, a Chinese medicine practitioner can help drive the temperature change seen in a BBT chart indicative of fertility [2].


There are SO many factors which can influence your BBT and make a chart appear off.

  • Stress or anxiety
  • Alcohol
  • Lack of sleep (a minimum of 3 hours sleep is recommended for an accurate resting body temperature)
  • Illness
  • Medications
  • The weather
  • An unreliable thermometer

If you’re just not sure if you are ovulating, get yourself to a GP or pathology and request a progesterone blood test be taken seven days after you suspect you have ovulated.  Timing is everything for this test and although the standard is to measure on “day 21” this does not equate with seven days after ovulation for everyone!  Be specific about your request (or your demand if it comes to that).

If BBT charting tells me only that I HAVE ovulated, how do I predict my fertile window?

Watch this space… next post.

Best, Jenna.


  1. Diagnostic evaluation of the infertile female: a committee opinion.  Fertility and Sterility , Volume 103 , Issue 6 , e44 - e50
  2. Ried, K. Chinese herbal medicine for female infertility: An updated meta-analysis. Compelmentary Therapy Medicine 2015 Feb 23 (1): 116-128.

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